Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Using grafted vegetables for field production is relatively new practice in the United States. However, it is a common practice in Asian countries as well as other areas of the world.
Grafting involves selecting a rootstock that will confer some desired trait, usually resistance to a soil-borne disease. A scion plant is selected, normally the crop and variety with the horticultural traits desired. The scion is grafted onto the rootstock. For example, with tomatoes, a seedling is severed just above the cotyledon. The above-ground portion (scion) of a desired variety for harvest is secured to the root system (rootstock) of the disease-resistant seedling. Once the grafted transplants heal, they can be planted in the field for normal production.
Vegetables that have been successfully grafted include tomatoes, peppers, and eggplants and watermelons, cantaloupes, cucumbers, and other cucurbits.
Grafting can be effective as a non-chemical control method for many soilborne diseases such as Verticillium wilt and Fusarium wilt in tomatoes, Fusarium wilt in watermelons, and root knot nematodes in tomatoes and cucurbits.
Grafting onto vigorous rootstocks can also allow plants to be more stress tolerant because the rootstock has a greater rooting area. This will allow for better water stress and heat tolerance.
Grafting can also improve overall productivity of crops when no disease or stress is present. Again, the vigorous root systems can improve overall nutrient and water uptake and increase fruit yields. In watermelons, rootstocks have been shown to improve fruit quality and holding ability in the field.
Much research is underway on grafted vegetables throughout the region and several growers have started to use grafted plants for production.